As traders on Wall Street send stock markets swooning one day and bring them back the next, many investment pros have common advice about what the rest of us should do: nothing.

Investment advisers said Friday that workers worried about the stocks in their 401(k) retirement plans are better off sitting tight than jumping in to change their investment mixes or sell their stock portfolios, ending up with cash or low-interest bonds that don't even have a chance of growing.

After the Dow Jones industrial average tumbled more than 500 points Thursday, the market swung wildly again Friday but ended with the Dow up 61 points and the broader Standard & Poor's 500 virtually unchanged.

"Investors are extremely skittish," said John Sawyer, chief investment officer at BBVA Compass, which has $19 billion in assets. "If you're watching this thing month to month and day to day, it's a very nerve-racking ride."

Big sell-offs could continue, he warned.

"Volatile events tend to cluster," said Sawyer, who pointed out that overall corporate earnings are good despite the weak economy. "It's not likely that this is the only movement like this that we'll see in either direction.

"It literally is a bit of talking them down," said Suzette Jones, an executive vice president at Amegy Bank, which has $11 billion in assets. "Investors need to plan for this inevitable roller coaster ride."

She said Amegy's eight-member asset allocation committee huddled Thursday afternoon and decided it was still convinced it was on the right path focusing on the economy's positive points, including decreasing oil prices.

The nature of the market

Investors braced for bad news in a jobless report Friday, but it showed that the economy added more jobs in July than expected.

"The bottom line is that these types of pullbacks and corrections are the nature of the stock market," said Jim Kee, president and chief economist of San Antonio-based South Texas Money Management, which has more than 1,000 clients and manages about $2 billion in assets. "They can't be predicted with any regularity. That's why everyone needs an investment plan."

That means disciplined allocations among stocks, bonds and other kinds of investments.

When the stock market becomes as volatile as it has this week, Kee said, the biggest mistake investors can make is to revisit or revise their investment plans and move money from one category to another.

"History shows investors are far better off staying with their investment plans through these sorts of big-sentiment swings," Kee said. "It's best not to be active by getting into or out of stocks."

Kee cited the 2008 stock market plunge.

"That was one of the worst in history. Investors would have been fine if they did nothing. The only time investors lose is when they sell at the bottom. That makes them unable to participate in the rebound," he said.

Hunting for bargains

Kevin Holt, a senior portfolio manager with Invesco in Houston, said now may be a good time for long-term investors to take advantage of lower-priced stocks.

He's been looking at sectors that may have been unfairly punished, such as media and bank stocks, in what he considers a market overreaction to global uncertainty.

"People are being overly negative. It's a tough situation, what's going on in a number of countries such as Greece and Spain, but we think the governments over there will be able to manage that," he said.

The European uncertainty, the long fight before Congress agreed to raise the U.S. debt ceiling and an unemployment rate over 9 percent have created angst amongst investors.

But for the most part, corporate balance sheets are in good shape with little debt, Holt said.

"It's my view that we're in for a sustained period of slow growth. That doesn't mean no growth, just slow growth," he said. "The market got a little too negative and sold off, and this will allow the system to rebalance."